Cooling system

ABSTRACT

A series-loop cooling system for cooling individually several zones within a building or several buildings includes a closed circuit having for each zone and within series in the circuit the heat exchange coil of a heat exchange unit which utilizes and incorporates the standard structural members of a building or of several buildings. A cooling medium is circulated continually through the circuit and the heat exchange coil of each heat exchange unit and thermostatically controlled fans in each heat exchange unit are adapted to pass air over the heat exchange coils and distribute the same into the temperature controlled zones.

United States Patent Piper 1 Sept. 12, 1972 1 1 COOLING SYSTEM [72] Inventor: James R. Piper, 6405 W. Chartres Dr., Palos Verdes, Calif. 90274 22 Filed: Feb.11, 1970 [21] Appl.No.: 10,418

52] us. c1. ..165/22,l65/39, 165/48 51 Int. Cl. ..B60h 1/00 [58] FieldofSearch ..l65/22,50,26,25,48,59

[56] References Cited UNITED STATES PATENTS 3,074,477 l/l963 Whalen ..l65/50 3,351,128 11/1967 Bamd ..l65/50 Primary Examiner-Charles Sukalo Attorney-Lyon 8; Lyon [57] ABSTRACT A series-loop cooling system for cooling individually several zones within a building or several buildings includes a closed circuit having for each zone and within series in the circuit the heat exchange coil of a heat exchange unit which utilizes and incorporates the standard structural members of a building or of several buildings. A cooling medium is circulated continually through the circuit and the heat exchange coil of each heat exchange unit and thermostatically controlled fans in each heat exchange unit are adapted to pass air over the heat exchange coils and distribute the same into the temperature controlled zones.

20 Claims, 6 Drawing Figures PAIENT ED SE? 12 I972 SHEET 2 OF 3 COOLING SYSTEM The invention relates to a system for cooling a plurality of separate zones within a building or several buildings and, in particular, to a system for circulating air past heat exchange coils and distributing the same throughout these zones.

Cooling systems normally used by todays building industry are expensive because of the cost of the equipment for such systems and the cost of installing these systems which normally required extensive alterations of the building structures. Series-loop hydronic cooling systems have performed well in the past, and are desirable from a cost standpoint, however, their use has been limited because such systems have previously been considered to be impractical for use in several buildings or in a large building, such as a large apartment house, because of the wide temperature differential required throughout these several buildings or through the large building. Moreover, past series-loop cooling systems have also failed to fully utilize the standard building structures and thereby further lower the cost of installation.

Therefore, it is a primary object of this invention to provide a series loop hydronic cooling system which will meet the varying demand associated with several buildings or a single large building.

Another object of this invention is to provide a cooling system for a building or several buildings which will incorporate into the system structural members essential to the construction of the building or buildings.

A further object of this invention is to provide a cooling system for a building or buildings with individually controlled temperature zones.

A still further object of this invention is to provide a cooling system having a closed circuit, through which a cooling medium continuously circulates, which avoids the use of valves or other similar mechanisms to control and divert the flow of the cooling medium in the circuit.

Another object of this invention is to provide a cooling system which will adjust to operate efficiently and economically when varying demands are made on the entire system and/or when varying demands are made on portions throughout the system.

In accordance with these and other objects, the cooling system of this invention includes a valve free closed circuit having in series the heat exchange coils of a plurality of heat exchange units. The system also includes pumps which cause a cooling medium to be continually circulated throughout the circuit and through each heat exchange coil and chiller units spaced at predetermined intervals about the circuit to maintain the temperature of the cooling medium in the circuit within desired limits. The heat exchange units of the system provide individually controlled temperature zones and each unit includes a thermostatically controlled fan which is adapted to pass air over and around a heat exchange coil and then distribute the air throughout a zone when cooling that zone.

Still another object of this invention is to provide a cooling system for a building or several buildings which is easy and relatively inexpensive to install and which utilizes low cost equipment having minimum maintenance requirements.

Other and more detailed objects and advantages of this invention will readily appear from the following detailed description and the accompanying drawings.

In the drawings:

FIG. 1 is a diagrammatic view illustrating a typical preferred form of the system.

FIG. 2 is a diagrammatic view showing a chiller unit used in the system.

FIG. 3 is a perspective view partially in section illustrating a heat exchange unit of the system.

FIG. 4 is a top plan view of a heat exchange coil of the heat exchange unit.

FIG. 5 is a front view of the heat exchange coil taken on the lines 5-5 of FIG. 6.

FIG. 6 is a side view of the heat exchange coil taken on the lines 6-6 of FIG. 4.

Referring now in detail to the drawings, the cooling system, generally designated 10, includes a closed loop circuit 11, which provides for communication of the cooling medium, preferably water, in the circuit throughout the building or buildings. While only a single system 10 has been shown it should be recognized that in some instances it may be desirable to employ more than one complete system 10 in a single building or more than one for the several buildings even though this single system 10, is adapted to accommodate a great many controlled temperature zones.

Preferably, plastic piping is employed in the circuit although other forms of pipe and tubing, including copper may be used. Also, as will be made apparent from the following discussion, the diameter of the piping is relatively small and because of the design of the system the amount of piping is held to a As seen in FIG. 1, the circuit 11 includes a train of heat exchange coils 12, the detail of which will be described later, a number of standard centrifugal pumps 13 and a number of chiller units 14. The coils 12 and the pumps 13 are connected to the circuit 11 in series, while the chiller units 14, which are also tied together with the circuit, are a closed completely separate system.

Normally, the number of pumps 13 and the number of chiller units 14 are the same, with each pump connected to the circuit in some instances where the circuit 11 required is particularly lengthy, for example when the system is used to cool several buildings which are located far apart, more pumps 13 than chiller units 14 may be desirable. Preferably, the pumps 13 are adapted to maintain the flow of the cooling medium in the circuit 1 1 at about 25-40 gallons per minute.

The chiller units 14 are generally equally spaced throughout the circuit 11 and normally, there is one chiller unit 14 required for every 10 or 12 coils, with each chiller unit 14 having an output of 120,000 BTUs. However, because of the varying demand of different type buildings, the number coils 12 per chiller unit 14 may range from as few as eight to as many as 20. However, the total output of BTUs required per coil in a system varies depending on the geographical area of use of the system, that is, in hotter areas, where there will be a greater temperature differential between the outside temperature and the desired zone temperature, a greater BTU output for the system can be increased by merely adding another chiller unit 14in series to any other chiller unit 14 in the system.

The chiller of a chiller unit 14 is seen best in FIG. 2. Each chiller 15 is of a relatively conventional gas powered type wherein the refrigeration cycle includes a closed ammonia-water cycle for cooling a tank of plain water. The chiller 15 includes a chiller tank 16 which chills the water in the chiller 15. In practice, this tank 16 is generally open to the atmosphere because the typical building and safety regulations require that any leaking ammonia be free to evaporate into the atmosphere, because, among other things, ammonia in water in a normal piping system will cause corrosion and failure. Also included within the chiller 15 is a chiller pump 17 which pumps the chilled water from the chiller tank 16 through a supply conduit 18 into a heat exchanger 19 where heat is absorbed from the water passing therethrough in the circuit 11 but which does not allow communication between the water in the circuit 11 and the water from the chiller unit 14. A return conduit 20 returns the heated water from the heat exchanger 19 to the chiller tank 16 of the chiller 15. The chiller 15 also includes an ambient thermostat 21 which controls the operation of the chiller 15 to maintain the temperature of the water in the chiller 15 and a thermostat control and sensor unit 22 which senses the temperature of the water in the circuit 11 immediately after it has passed through the heat exchanger 19. Preferably, the temperature of the water sensed by the sensor unit 22 should be about 45 and when the temperature falls below a predetermined minimum temperature the chiller pump is shut off.

As stated previously, each controlled temperature zone includes a heat exchange unit, generally designated 30, and shown in detail in FIG. 3. Each heat exchange unit includes within it one of the heat exchange coils 12. The heat exchange coil is mounted between a pair of the normal parallel structural members or floor joists 31 near one end of a room in a building. Opposite the heat exchange coil 12 and also mounted between the same joists 31 at the other end of a room is a partition wall 32. The partition wall 32 is provided with an opening 33 which acts as an inlet for air. The floor 34 of the room and an enclosing cover member 35 form a plenum 36 between the heat exchange coil 12 and the partition wall 32, with the joists 31 acting as the side walls of the plenum 36. An electric fan 37 is connected to the other side of the partition wall 32 outside the plenum 36. The fan 37 is operated by a thermostat control 38 which is located in the controlled temperature zone. The outlet of the fan 37 is connected to the inlet opening 33 of the partition wall 32 to provide a passage for air between the fan 37 and the plenum 36. The plenum is sufficiently large in order to provide a slow air movement which causes improved heat transfer between the air and the heat exchange coil 12 and also causes less air disturbance in the area to be cooled. All the air passing through the plenum 36 must pass over the heat exchange coil 12 before entering the area to be cooled.

An inlet air flow register, not shown, and an outlet air flow register 38 are located between the joists and on the floor 34 at opposite ends of the room. The inlet air flow register allows warm air to be drawn from the controlled temperature zone by the fan 37 while air flow register 38 allowed the cooled air to pass from the plenum into the zone.

The heat exchange coil 12, as seen best in FIGS. 4 through 5, includes an inlet line 40 and an outlet line 41. The inlet and outlet lines 40 and 41 are parallel to each other, and the open end 42 of the inlet line 40 and the open end 43 of the outlet line 41 are connected to the circuit 11. The coil 12 also includes a plurality of parallel U-tubes M which are connected in parallel at one end 45 to the inlet line 40 and at the other end 46 to the outlet line 41. Each U-tube 44 extends downwardly on an incline from the inlet line 40 to a U- bend 47 and upwardly on an identical incline from the U-bend 4,7 to the outlet line 411. Mounted laterally across the U-tubes 44 are a plurality of parallel radiation fins 48. The U-tubes 44 are positioned within a housing 49 which includes parallel side walls 50 and 51, and bottom and top cover plates 52 and 53, with the front and back ends 54'and 55 of the housing 49 open. The sidewalls 50 and 51 and the top cover plate 53 cooperate to form a pair of horizontal flanges 56 and 57 which are adapted to rest on the top of the joists 31 with the sidewalls 50 and 51 fitting tightly along the sides of the joists 31. An air directing plate member 58 extends laterally across the U-tubes 441 and is connected along the upper side to the cover plate 53. The fins 48 are positioned on the U-tubes 44 between the air directing member 58 and the U-bends 47, which are located near the bottom cover plate 52, and thereby define a heat transfer area through which substantially all the air flowing in the plenum 36 must pass. Inlet line 40 and an outlet line 41 are extended out from the housing 49 through openings in the sidewalls 51 and 50, respectively. When mounting the heat exchange coil 12 between the joists, a notch 60 is cut into the upper end of each joist to allow the inlet line 40 and the outlet line 41 to pass therethrough. Preferably, the U- tubes 44, the inlet 40 and the outlet line 41 are formed of copper, however, other materials are suitable. Also, in the preferred form the housing 49 is galvanized sheet steel and the fins 48 are aluminum. it should be noted that a significant feature of the heat coil 12 is that any water entering the coil 12 through the inlet line 40 travels the same distance before it exits out the outlet line 41 irrespective of which U-tube the water chooses to travel between the inlet line 40 and outlet line 41. Moreover, the plurality of narrow U-tubes provide a heat transfer area which will accommodate a large volume of air flow.

The operation of the system 10 is as follows:

Water in the circuit 11 is continually circulated throughout the closed circuit 11 and through each coil 12 by the pumps 13. The low temperature of the water is maintained within preferred limits by the chiller units 14 which cause chilled water to be passed to heat exchangers 19 through which the water in the circuit passes at various predetermined locations in the circuit 11. it has been found that under normal conditions when chiller units 14' having an output of 120,000 BTUs are located in the circuit 11 at intervals with 10 or 12 heat coils 12 between each chiller unit 14, the water in the circuit 11 generally increases in temperature only about 8F under maximum demand when it passes from one chiller unit 14 to another. Maximum demand is the situation where cooling is required in all the controlled temperature zones of the system. It should be evident that in a system having several controlled temperature zones this situation rarely arises, because among other reasons, it is unlikely that all of the zones will be occupied and thereby require cooling at any given time. Another interesting aspect of systems having several controlled zones is that not only will the total demand on the system vary, but it may also vary throughout portions of the system. However, this system readily adapts to such variations because of the segmenting of the chiller equipment.

Temperature control in a zone is achieved by the heat exchange unit 30 located in that zone. Each heat exchange unit 30 operates independently and when cooling is desired in a particular zone, the thermostat control 38 in that zone activates the electric fan 37 which draws hot air from the zone through the inlet air flow register and forces it through the plenum 36 and across the heat transfer area of the heat exchange coil 12 where heat from the air is absorbed. The cooled air then passes out through the outlet airflow register 38 into the zone. When that zone is sufiiciently cooled, the thermostat turns off the fan 37 and the flow of cool air into the room discontinues. The cold water in the circuit 11 continues to circulate through the heat exchange coil 12, but temperature of the room remains unaffected when the fan is stopped due to the relatively low temperature differential from the coil to the room and the insulation therebetween whereby heat transfer is minimal.

Segmenting of the chiller equipment as stated before is an important feature of this invention because of the variation in the demand throughout the system. However, it should also be noted that this so called segmenting has many other advantages over a system with a single large chiller unit. The use of the smaller units avoid the necessity of the relatively large piping of a single unit. Moreover, the initial costs, the installation costs and the maintenance costs are generally lower where several small units are employed. In addition, a breakdown of one of the smaller chiller units of this system will not completely disable the entire system.

Furthermore, by setting the ambient thermostat 2l on one of the chiller units 14 at a lower maximum temperature than the settings of the ambient thermostats on the other chiller units 14, when there is only a small temperature differential between the temperature of the outside atmosphere and temperature desired in the controlled zones and thus a small total demand on the system only one of the chiller units 14, which is sufficient, will be operating.

This invention includes all the advantages previously recognized in a series loop system while avoiding several disadvantages thought apparent in such systems. This system has the advantage of a relatively low installation cost which is due in part to the utilization of the standard structural members into the system. Otherwise wasted space between the floor or ceiling joists is used to form a part of the system. Thus, ducts as normally conceived are not required. In addition, since this system is a series loop system the length of pipe the system requires is held to a minimum. Moreover, the cooling medium is circulated throughout the system without the need for expensive valve controls.

This invention provides a relatively low cost cooling system which includes individually controlled temperature zones. It is particularly adapted for use in large buildings or for use in several small buildings and it operates at a high efiiciency.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details herein set forth, but my invention is of the full scope of the appended claims.

I CLAIM:

l. A cooling system for cooling separately a plurality of zones in a building or buildings, comprises: a single continuous closed loop circuit for communication of a cooling medium therethrough; a plurality of heat exchange coils, at least one for each zone, all including an in series connection with said closed loop circuit; continuously operating pump means connected in series in said closed loop circuit for circulating the cooling medium through each said heat exchange coil and continuously around said closed loop circuit; segmented chiller means for maintaining said cooling medium throughout said closed loop circuit within a predetermined temperature range by extracting heat from said cooling medium according to the total demand on the system and according to varying demands throughout different portions of the system, said segmented chiller means comprising a plurality of independently operable chiller units, each said chiller unit having a heat exchanger, and said heat exchangers positioned at predetermined locations throughout said closed loop circuit and being adapted to cause heat to be absorbed from the cooling medium in said closed loop circuit; and selectively operable air circulating means associated with each said heat exchange coil for passing air over said heat exchange coil and into a zone where cooling is desired.

2. The system of claim I, wherein each said chiller unit includes at least one conventional gas operated chiller, said chiller having a closed refrigerant cycle for chilling liquid vented to atmosphere, said chiller thereby being adapted to communicate substantially refrigerant free chilled liquid to said heat exchanger for absorbing the heat from the cooling medium in said closed loop circuit.

3. The system of claim 1, wherein each said chiller unit is controlled by a thermostat which senses the temperature of the cooling medium after it passes said heat exchanger.

4. The system of claim 1, wherein said chiller means is adapted to maintain the cooling medium at about 45 5. The system of claim 1, wherein said pump means comprises a plurality of centrifugal pumps.

6. The system of claim 1, wherein said air circulating means is an electric fan operated by a thermostat control responsive to the air temperature in the zone in which the temperature is to be controlled.

7. A cooling system for a building or buildings adapted to cool a plurality of separately controlled temperature zones within the building or buildings, comprising:

a single continuous closed loop circuit for communicating a cooling medium;

a plurality of heat exchange coils for cooling air including an in series connection with said loop circuit;

a plurality of chiller units for maintaining the water in said loop circuit at a predetermined temperature, each said chiller unit being independently operable whereby the number of chiller units operating at any one time may vary according to the demand on the system;

pump means for circulating the water through each said heat exchange coil and continuously around said loop circuit and connected in series in said loop circuit; and

independently and selectively operable heat exchange units for providing cooled air to the zones, each said heat exchange unit including one of said heat exchange coils and air circulating means associated with said heat exchange coil being adapted to pass air over said heat exchange coil into a zone requiring cooled air.

8. The system set forth in claim 7, wherein each said chiller unit includes an ambient thermostat control.

9. The system set forth in claim 7, wherein said chiller units are located about said loop circuit at predetermined spaced locations and a predetermined number of heat exchange coils are connected to said loop circuit between each said chiller unit.

10. The system set forth in claim 7, wherein said chiller units each have an output of about 120,000 BTUs and the number of heat exchange coils between each said chiller unit ranges from 8 to 20 ii. The system set forth in claim 10, wherein said pump means is adapted to maintain a flow rate of the water in said loop circuit of about 25 to 40 gallons per minute.

- 112. The system set forth in claim 7, wherein said pump means comprises a plurality of pumps, with at least one of said pumps associated with each said chiller unit.

13. The system set forth in claim 7, wherein said air circulating means is an electric fan operated by a thermostat control responsive to the air temperature in a controlled temperature zone.

14. The system set forth in claim 7, wherein means are provided to separate each said heat exchange coil from the controlled temperature zones thereby preventing any significant heat transfer to the zones when said air circulating means is not operating.

15. The system set forth in claim 7, wherein said chiller units are adapted to maintain the water in said loop circuit at about 45 F.

16. The system set forth in claim 7, wherein each said heat exchange unit includes a plenum for directing the air from said air circulating means over said heat coil, each said plenum being formed in part by a'pair of conventional structural members of a building which are positioned in a spaced and parallel relation, such as joists and studs.

117. The system of claim 16, wherein said air circulating means and said heat exchange coil in each said heat exchange unit are mounted within and directly between said pair of conventional structural members forming in part said plenum.

18. The system set forth in claim 7, wherein each chiller unit includes a heat exchanger, said chiller unit having a closed refrigerant cycle and a chiller cooling medium ,cycle vented to atmosphere, and said chiller unit th reb be'n ada ted to irculate sad se aratel maintained chill coo ing me ium in sai loop circuix is absorbed by the chiller cooling medium when the cooling medium in said loop circuit passes through said heat exchanger.

19. The system set forth in claim 18, wherein each chiller unit includes a thermostat control unit, which senses the temperature of cooling medium in said loop circuit, said thermostat control unit controlling the circulation of the chiller cooling medium into said heat exchanger.

20. A temperature control system adapted to individually control a plurality of separate temperature zones, comprising: a single continuous closed loop circuit for communicating water; a plurality of heat exchange coils; means for maintaining the water in said circuit at a predetermined temperature, said means comprising segmented chiller means adapted to extract heat from the water according to the total demand on p the system and according to varying demands throughout different portions of the system, said segmented chiller means including a plurality of independently operable chiller units, each said chiller unit having a heat exchanger, and said heat exchangers positioned at predetermined locations throughout said closed loop circuit and being adapted to cause heat to be absorbed from the water in said closed loop circuit; pump means connected in series in said circuit for circulating the water through each said heat exchange coil and continuously through said circuit; a selectively operable heat exchange unit for providing air to the zones, each said heat exchange unit including one of said heat exchange coils and air circulating means associated with said heat exchange coil being adapted to pass air across said heat exchange coil; and each said heat exchange coil having an inlet line connected to said circuit and an outlet line connected to said circuit, said inlet and outlet lines each having an open inlet and outlet end respectively, a plurality of U-tubes forming a relatively large heat transfer area and connected to said outlet line and said inlet line with the total sum distance from said connection with said inlet line to said inlet end and from said connection with said outlet line to said outlet end being equal for each said U-tube whereby any water entering said coil travels the same distance before exiting irrespective of which said U- tube the water travels from said inlet line to said outlet line. 

1. A cooling system for cooling separately a plurality of zones in a building or buildings, comprises: a single continuous closed loop circuit for communication of a cooling medium therethrough; a plurality of heat exchange coils, at least one for each zone, all including an in series connection with said closed loop circuit; continuously operating pump means connected in series in said closed loop circuit for circulating the cooling medium through each said heat exchange coil and continuously around said closed loop circuit; segmented chiller means for maintaining said cooling medium throughout said closed loop circuit within a predetermined temperature range by extracting heat from said cooling medium according to the total demand on the system and according to varying demands throughout different portions of the system, said segmented chiller means comprising a plurality of independently operable chiller units, each said chiller unit having a heat exchanger, and said heat exchangers positioned at predetermined locations throughout said closed loop circuit and being adapted to cause heat to be absorbed from the cooling medium in said closed loop circuit; and selectively operable air circulating means associated with each said heat exchange coil for passing air over said heat exchange coil and into a zone where cooling is desired.
 2. The system of claim 1, wherein each said chiller unit includes at least one conventional gas operated chiller, said chiller having a closed refrigerant cycle for chilling liquid vented to atmosphere, said chiller thereby being adapted to communicate substantially refrigerant free chilled liquid to said heat exchanger for absorbing the heat from the cooling mediUm in said closed loop circuit.
 3. The system of claim 1, wherein each said chiller unit is controlled by a thermostat which senses the temperature of the cooling medium after it passes said heat exchanger.
 4. The system of claim 1, wherein said chiller means is adapted to maintain the cooling medium at about 45* F.
 5. The system of claim 1, wherein said pump means comprises a plurality of centrifugal pumps.
 6. The system of claim 1, wherein said air circulating means is an electric fan operated by a thermostat control responsive to the air temperature in the zone in which the temperature is to be controlled.
 7. A cooling system for a building or buildings adapted to cool a plurality of separately controlled temperature zones within the building or buildings, comprising: a single continuous closed loop circuit for communicating a cooling medium; a plurality of heat exchange coils for cooling air including an in series connection with said loop circuit; a plurality of chiller units for maintaining the water in said loop circuit at a predetermined temperature, each said chiller unit being independently operable whereby the number of chiller units operating at any one time may vary according to the demand on the system; pump means for circulating the water through each said heat exchange coil and continuously around said loop circuit and connected in series in said loop circuit; and independently and selectively operable heat exchange units for providing cooled air to the zones, each said heat exchange unit including one of said heat exchange coils and air circulating means associated with said heat exchange coil being adapted to pass air over said heat exchange coil into a zone requiring cooled air.
 8. The system set forth in claim 7, wherein each said chiller unit includes an ambient thermostat control.
 9. The system set forth in claim 7, wherein said chiller units are located about said loop circuit at predetermined spaced locations and a predetermined number of heat exchange coils are connected to said loop circuit between each said chiller unit.
 10. The system set forth in claim 7, wherein said chiller units each have an output of about 120,000 BTU''s and the number of heat exchange coils between each said chiller unit ranges from 8 to 20
 11. The system set forth in claim 10, wherein said pump means is adapted to maintain a flow rate of the water in said loop circuit of about 25 to 40 gallons per minute.
 12. The system set forth in claim 7, wherein said pump means comprises a plurality of pumps, with at least one of said pumps associated with each said chiller unit.
 13. The system set forth in claim 7, wherein said air circulating means is an electric fan operated by a thermostat control responsive to the air temperature in a controlled temperature zone.
 14. The system set forth in claim 7, wherein means are provided to separate each said heat exchange coil from the controlled temperature zones thereby preventing any significant heat transfer to the zones when said air circulating means is not operating.
 15. The system set forth in claim 7, wherein said chiller units are adapted to maintain the water in said loop circuit at about 45* F.
 16. The system set forth in claim 7, wherein each said heat exchange unit includes a plenum for directing the air from said air circulating means over said heat coil, each said plenum being formed in part by a pair of conventional structural members of a building which are positioned in a spaced and parallel relation, such as joists and studs.
 17. The system of claim 16, wherein said air circulating means and said heat exchange coil in each said heat exchange unit are mounted within and directly between said pair of conventional structural members forming in part said plenum.
 18. The system set forth in claim 7, wherein each chiller unit includes a heat exchanger, said chiller unit having a closed reFrigerant cycle and a chiller cooling medium cycle vented to atmosphere, and said chiller unit thereby being adapted to circulate said separately maintained chiller cooling medium in said loop circuit is absorbed by the chiller cooling medium when the cooling medium in said loop circuit passes through said heat exchanger.
 19. The system set forth in claim 18, wherein each chiller unit includes a thermostat control unit, which senses the temperature of cooling medium in said loop circuit, said thermostat control unit controlling the circulation of the chiller cooling medium into said heat exchanger.
 20. A temperature control system adapted to individually control a plurality of separate temperature zones, comprising: a single continuous closed loop circuit for communicating water; a plurality of heat exchange coils; means for maintaining the water in said circuit at a predetermined temperature, said means comprising segmented chiller means adapted to extract heat from the water according to the total demand on the system and according to varying demands throughout different portions of the system, said segmented chiller means including a plurality of independently operable chiller units, each said chiller unit having a heat exchanger, and said heat exchangers positioned at predetermined locations throughout said closed loop circuit and being adapted to cause heat to be absorbed from the water in said closed loop circuit; pump means connected in series in said circuit for circulating the water through each said heat exchange coil and continuously through said circuit; a selectively operable heat exchange unit for providing air to the zones, each said heat exchange unit including one of said heat exchange coils and air circulating means associated with said heat exchange coil being adapted to pass air across said heat exchange coil; and each said heat exchange coil having an inlet line connected to said circuit and an outlet line connected to said circuit, said inlet and outlet lines each having an open inlet and outlet end respectively, a plurality of U-tubes forming a relatively large heat transfer area and connected to said outlet line and said inlet line with the total sum distance from said connection with said inlet line to said inlet end and from said connection with said outlet line to said outlet end being equal for each said U-tube whereby any water entering said coil travels the same distance before exiting irrespective of which said U-tube the water travels from said inlet line to said outlet line. 